What has more recoil? - Does muzzle energy have any correlation to recoil?

[Aim1]

This maybe a stupid question but here goes.

If you fire 2 different bullets both with a muzzle velocity of 800 fps out of the same gun and one is 158gr. and one is 130gr., which one has more recoil?


Also, does muzzle energy have any correlation to recoil?

 

[troy fairweather]

The 158 will take more powder to go 800 fps over the 130, all other things being equal. So the 158 will have more recoil.

 

[rule303]

Newton's third law. Yes, all else being equal the heavier projectile will generate more recoil.

 

[JumboJVT]

Energy = Mass x Velocity(sq'd). Same V and higher M equals increased E. Increased E on one end equals increased E on the other: assuming no increase in the mass of the firing mechanism, equals more recoil. Physic don't allow it to be any other way. Different burn rate powders may produce different recoil pulses (i.e. E/time), but in the end total E for a heavier bullet is higher than for lighter, therefore more total recoil. But if the recoil pulse is spread over more time, it may "feel" like less recoil.

 

[Aim1]

Thanks for the replies guys.


Also, does muzzle energy have any correlation to recoil?

 

[film495]

Thanks for the replies guys.


Also, does muzzle energy have any correlation to recoil?

I'm not an expert, but from a simpleton's perspective of physics, the nrg going forward is equal to the nrg going backward as recoil. So, yeah - it is directly corollary. A .22 will have less recoil than a .223 in the same weight bullet - all other things being equal, gun weight etc, the one with higher muzzle energy will certainly produce more recoil, and felt recoil if the firearms weigh the exact same.

 

[Paco42]

Look again at #4. “Increased E on one end equals increased E on the other”. Assuming both firearms have the same mass, the muzzle energy of the projectile will have a strong correlation to recoil—assuming recoil = amount of work performed, generally as movement of the mass of the firearm. Again, if the work (recoil) is spread out over time, it may seem less, but the total work/recoil must remain the same. Until one gets down to subatomic considerations, Newton’s version of physics holds sway.

 

[jmr40]

There are 4 things that effect recoil

Weight of the projectile
Weight of the powder charge
Weight of the firearm
Velocity

In your case if we assume the firearm is the same weight and the velocity is the same the 158 gr bullet will have more recoil due to the weight of the projectile and the fact that it will need more powder. Normally when we go up in bullet weight the powder charge is lower and velocity is lower which helps cancel out the effect of the heavier bullet.

Play around here with some numbers to see how changes in any of the 4 factors change recoil.

http://www.shooterscalculator.com/recoil-calculator.php

does muzzle energy have any correlation to recoil?

Not really. It depends on all of the other factors. Some cartridges are more efficient than others. It is possible to get the same energy with a lot less recoil by using different bullet weights and powder charges.

For example you can load 308 and 30-06 to shoot the same bullet weights at the same velocity. But you'd still need a lot more powder in the 30-06 case. They would both have exactly the same velocity and energy. But the 308 will recoil less since it burned less powder to achieve the same speed.

Normally we'd use even more powder in 30-06 and get more speed than 308 for even more recoil. Just using this as an example to explain what is possible.

 

[denton]

The usual analysis of recoil comes from the Law of Conservation of Momentum. The momentum of firearm + cartridge before firing = momentum after.

If the firearm is free to recoil, the momentum of the rifle moving backward = momentum of the projectile and gas moving forward.

The amount of force on your shoulder is the rate at which the rifle is losing momentum. If you have a steel buttplate, the rifle is brought to rest quickly and felt recoil is high. With a recoil pad, it takes longer to bring the rifle to rest, and less recoil is felt.

 

[SteadyD]

In revolvers I almost always perceive heavier bullets to recoil more. The one exception is wadcutters which are loaded to such a slow velocity that the recoil is less. Oddly, in semi autos I perceive heavier bullets to have less recoil. Recoil is very subjective. Others here will likely dispute my perceptions.

 

[Jim Watson]

Denton is correct, recoil is a momentum balance, mass x velocity.
So while you could say recoil is correlated to energy, 1/2 mass x velocity squared, it is not simply correlated. You sure aren't getting two hundred foot pounds of kinetic energy from recoil of a .38 Special.

 

[ATLDave]

Momentum, not energy, is the driver of recoil.

 

[earplug]

The burning powder adds to the recoil. The expanding gases create thrust. We call it muzzle blast. Given equal kinetic energy a lighter bullet with a higher powder charge will generate more recoil, then a heavier bullet with a lower powder charge.
This is why heavier bullets are popular in action shooting games where a minimum power factor must be met.

 

[fxvr5]

The burning powder adds to the recoil. The expanding gases create thrust. We call it muzzle blast. Given equal kinetic energy a lighter bullet with a higher powder charge will generate more recoil, then a heavier bullet with a lower powder charge.
This is why heavier bullets are popular in action shooting games where a minimum power factor must be met.

You're confusing kinetic energy with momentum. With the same kinetic energy, the heavier bullet, even though traveling slower (and producing more momentum) will produce more recoil.

 

[earplug]

You're confusing kinetic energy with momentum. With the same kinetic energy, the heavier bullet, even though traveling slower (and producing more momentum) will produce more recoil.

I'm not confusing anything. The muzzle blast contributes to the felt recoil. Its how a rocket works.

 

[fxvr5]

I'm not confusing anything. The muzzle blast contributes to the felt recoil. Its how a rocket works.

No, seriously, you are. Look up the formula for kinetic energy (muzzle energy) and momentum (power factor).

 

[Paco42]

Denton is correct, recoil is a momentum balance, mass x velocity.
So while you could say recoil is correlated to energy, 1/2 mass x velocity squared, it is not simply correlated. You sure aren't getting two hundred foot pounds of kinetic energy from recoil of a .38 Special.

I’m not sure what you mean by “simply correlated”, but it’s simply a matter of physics that “for every action, there’s an equal and opposite reaction”. Actions occur due to a force, and in the realm in which classical physics most adequately applies, F = ma, where m = mass and a = acceleration. Force and energy when considered together are often thought of confusingly. Force is measured in units of mass x distance ÷ time squared—certainly somewhat awkward for most of us to grasp immediately. Energy (of the kinetic variety, that of interest here) is expressed in units of mass x distance squared ÷ time squared. (Velocity technically includes direction, but for simplicity we’ll equate velocity with speed, and say that v = speed = distance/time.) Kinetic energy = KE = 1/2 x mass x velocity squared. Thus, force and energy, while not exactly the same thing, are closer than kissin’ cousins.

The force applied to the mass of the bullet for that bullet to be accelerated to the point where it has a given kinetic energy must, by Newton’s Third Law, be equal to an opposite force—that applied to the case, powder remnants and expelled gases, the gun, including the slide and spring(s) of a semi-auto, the hands and body of the shooter, etc. It may not be easy to see (or feel) where it goes, but it goes somewhere. And the correlation of recoil to energy isn’t weak, it’s quite strong. Which is exactly why bullseye competition shooters, for instance, use light loads with wadcutters—by reducing the energy of the cartridge, they reduce felt recoil. Now, how one goes about measuring felt recoil, and dissipating the energy that comprises it, and various other factors all come into play when shooters discuss the perceived differences in recoil from one load to another, one gun to another, etc.

 

[Jim Watson]

Nope. Energy does not have a vector (directional) component, momentum does, and conservation of momentum is the basis for determining recoil.
In the end the energy of the chemical bonds in the gunpowder winds up largely as heat.
If you follow it through, the momentum of the bullet and the equal but opposite momentum of the recoiling gun are transmitted to the planet where they cancel out.

 

[MistWolf]

I'm not confusing anything. The muzzle blast contributes to the felt recoil. Its how a rocket works.

While you are correct that the gasses add to recoil (that's why brakes work- they change the direction of the blast), what we are talking about is free recoil (which is measurable and calculable) not felt recoil (which is subjective).

From SAAMI-

FREE RECOIL ENERGY
Recoil can be described mathematically by the physical law of the Conservation of Momentum.
The law states: "If a force and its reaction act between two bodies, and no other forces are
present, equal and opposite changes in the momentum will be given to the two bodies." Simply
stated, this says that for every action there is an equal and opposite (in direction) action. It must
be noted this approach does not consider any impact on free recoil due to the redirection of
propellant gases by attached devices such as muzzle brakes or suppressors. Felt recoil (also
referred to as “Perceived” recoil) can also vary by modifying the rate of application of force by
devices such as recoil pads or damping devices and the influence of action type.

The momentum, therefore, of a free recoiling firearm is equal and opposite in direction to the
momentum of the bullet (or shot charge/slug and wad column) and the propellant gases.
Because the propellant gases are extremely difficult to weigh, for purposes of this application,
the propellant gas weight will be equated to the powder charge weight.

Link to the PDF- https://saami.org/wp-content/uploads/2018/07/Gun-Recoil-Formulae-2018-07-9-1.pdf

 

[Jim Watson]

Because the propellant gases are extremely difficult to weigh, for purposes of this application,
the propellant gas weight will be equated to the powder charge weight.

That's not a problem, except for a few unburnt granules left in the gun, all the powder is converted to gas and blows out behind (and around) the bullet.
The trick is that

The effective velocity of the propellant gas, a much more difficult measurement, varies, in general, with the muzzle pressure and projectile velocity.

I presume that the rule of thumb multipliers were determined by firing tests in a ballistic pendulum. Close enough for government work, especially with pistols. Less precise for a rifle with powder half the mass of the bullet.

 

[MistWolf]

That's not a problem, except for a few unburnt granules left in the gun, all the powder is converted to gas and blows out behind (and around) the bullet.

The mass of the gas and ash is equivalent to the mass of the powder.

As for the velocity of the the gas of smokeless powder, I think they use a constant of 5700 fps for calculating free recoil.

 

[Jim Watson]

The SAAMI page you linked shows a multiplier for each class of firearm; 1.75x bullet velocity for a rifle, 1.5x for a pistol.
The version I recall from print gunzine days was 4500 fps in general.

 

[denton]

Hatcher used a SWAG that the peak speed of the escaping gas at the muzzle was twice the speed of the bullet. I'm of the opinion that 3X may be a better estimate, but that's JMO, based on the nature of exponentially decaying processes.

I suppose there is a way to actually make that measurement, but I'm not aware of anyone who has.

We know what the average speed is because we can measure the recoil momentum of the rifle, and that has to be equal to the momentum of the bullet plus the momentum of the gas. With a scale and chronograph, we can get the momentum of the bullet. The difference between the rifle and the bullet is the momentum of the gas. The mass of the gas is just the mass of the powder. So it is easy to solve for the average speed of the gas.